Controlling the start of injection in self-igniting internal combustion engines is just as important as controlling the initiation of ignition in Otto engines. These variables have a critical influence on engine output and behavior and on the exhaust gas composition. The principles and effects of controlling the injection start have long been known. With a view to rising energy costs and increasingly stringent regulations for the composition of the exhaust gas, however, it is important to make this control more precise and to optimize it.
From German Offenlegungsschrift No. 26 53 046 (U.S. Pat. No. 4,265,200), an injection start controlling device is known in which a set-point value dependent on operating characteristics is formed, this set-point value is compared with a measured actual value, and the difference between the two values is subjected to a control process. The essential feature of this known injection start controlling device is a reference marking on the crankshaft prior to the latest possible onset of injection. The crankshaft increments until the actual value of the injection start are counted with respect to this reference marking and processed by closed-loop control techniques.
The known device requires two sensors, one for the reference marking and one for the crankshaft angle increments. For mass production at favorable expense or cost, this dual sensor has proven too expensive, and it is, therefore, one of the objects of the invention to create an injection start controlling means having one sensor which is simple and reliable.